1. Field of the Invention
This invention relates generally to wood comminuting machines, such as tub grinders, horizontal feed grinders, gravity-fed grinders, or the like, and more particularly to rotor assemblies including inserts for reducing wood product into cuts or chips.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
Wood grinding or chipping machines typically have hammers mounted on rotors. Replaceable hammer inserts with cutters are supported on the rotors for cutting or fragmenting wood product. The rotors rotate about a common longitudinal axis to bring the hammer inserts into cooperation with at least one anvil spaced radially outward from the inserts. As each hammer insert passes the anvil, the wood product is cut between the insert and the anvil. The hammer inserts are commonly coated with a welded-on hard, abrasive wear material, such as tungsten carbide, to facilitate cutting the wood product and to provide the inserts with a longer useful life. Ultimately, the wear material abrades during use, particularly at cutting edges of the inserts that pass nearest the anvil. As a result, the inserts must be replaced on a regular basis to maintain their ability to provide an efficient reduction of the wood product. This increases the cost of the wood product reduction process.
To increase their useful lives hammer inserts are known to include pairs of cutting edges disposed at opposite ends of each insert. When one cutting edge of an insert located in an active cutting position is worn out, the insert can be detached, rotated, and reattached to position the remaining cutting edge in the active cutting position.
To increase their effectiveness in cutting and fragmenting wood, hammer inserts are known to include cutting edges defined by pairs of facets that converge to form a diagonally outwardly directed radially distal corners positioned to pass very close to an anvil when in the active cutting position. However, the facets form acute angles of less than 60 degrees leaving very little material thickness to support the welded-on abrasive wear material coating.